chore(*): add display-density

Author: MonikaKirkova

samples/grids/tree-grid/data-summaries-custom/index.html

@@ -24,6 +24,7 @@
         auto-generate="false"
         name="treeGrid"
         id="treeGrid"
+        display-density="compact"
         primary-key="ID"
         foreign-key="ParentID">
             <igc-column

samples/grids/tree-grid/data-summaries-custom/src/index.css

@@ -1,6 +1,2 @@
 /* shared styles are loaded from: */
 /* https://static.infragistics.com/xplatform/css/samples */
-
-.container {
-    --ig-size: var(--ig-size-small);
-}